This invention relates to a sealing arrangement and method, which may be used for forming a seal between two surfaces, for example in a protective housing to protect the contents of the housing from contamination, or within a domestic appliance or other device to prevent fluids from penetrating into parts where they would cause nuisance or damage.
Many kinds of seal are known for forming a seal between two surfaces. Typically a sealing member is positioned between two surfaces, and the surfaces are then brought towards each other, causing the sealing member to be compressed and thereby urged into sealing engagement with both of the surfaces. Generally seals of this type fall into two main categories. The first category are so-called axial seals, in which the sealing member is generally compressed in the same direction as the direction of relative movement of the two surfaces being brought towards each other. The second category are so-called transverse seals (often radial seals depending on the orientation of the parts), in which the sealing member is generally compressed in a direction transverse (often perpendicular) to the direction of relative movement of the two surfaces which are being brought towards each other. The present invention relates to a transverse seal.
One example of a known transverse sealing arrangement is a radial seal applied as an O-ring between a base and a dome shaped housing in a closure for telecommunications cables. The base has a generally circular flat surface and an upstanding rim around its edge. The O-ring is shaped to fit around the outside of the rim. The dome shaped housing has a diameter which is larger than that defined by the rim of the base, but smaller than that defined by the inner circumference of the O-ring when in position on the base, and in an uncompressed state. Therefore, as the dome shaped housing is brought down onto the base, the ring is compressed radially inward between the housing and the rim. In this prior art, as in most transverse (e.g. radial) seals, the direction of compression (in this case radially inward) is perpendicular to the direction of relative movement of the surfaces that are being brought towards each other (in this case axial movement between the base plate and the housing).
Another example of a known radial seal is a V-shaped seal. This may be arranged, for example on the base and dome shaped housing structure described above, so that one arm of the xe2x80x9cVxe2x80x9d seal is secured to the inner wall of the rim of the base, and the closed tip of the xe2x80x9cVxe2x80x9d seal points towards the approaching dome shaped housing. As the dome shaped housing is brought towards the base, the other arm of the xe2x80x9cVxe2x80x9d seal is urged into sealing engagement with the dome shaped housing.
Sealing arrangements in which one of the surfaces being sealed comprises a channel shaped portion, and sealing arrangements in which the two surfaces being sealed comprise tongue and groove shaped portions, are known. WO-A-96/18836 (N.V. Raychem S.A.), for example, describes a seal comprising a flexible tubular, elastomeric article having a series of surface depressions on its outer surface which generally contain or/and are coated with a sealing gel. In one example the housing parts comprise a channel and a lid, and the seal is shaped and sized so that it initially is a loose fit within the channel. The lid is brought towards the channel causing the elastomeric article to deform so that the gel forms a seal against the floor of the channel and the lid, and may also seal against the side walls of the channel. This therefore forms both an axial seal (between the floor of the channel and the lid), and a radial seal (if the gel also seals against the side walls). As another example, WO-A-96/09483 describes a tubular layer of a gel sealant on a flexible tubular carrier used as a sealing member. It may be compressed in any convenient manner, e.g. in a tongue and groove joint. In one example shown, the seal is placed loosely in a groove, and then a tongue shaped portion introduced to compress the seal.
We have discovered a new sealing arrangement, which in its various embodiments has several advantages over sealing arrangements known hitherto.
A first aspect of the present invention provides a method of forming a seal between two housing parts, at least a first one of which comprises a channel shaped portion; the method comprising:
i) providing a sealing member that prior to sealing has a transverse dimension that is greater than a transverse dimension of the channel shaped portion;
ii) positioning the sealing member adjacent to the channel shaped portion; and
iii) moving the second housing part relative to the channel shaped portion, causing the sealing member to be inserted into the channel shaped portion of the first housing part, and thereby compressed in its transverse dimension.
A second aspect of the present invention provides a sealing arrangement comprising:
i) two housing parts, at least a first one of which comprises a channel shaped portion;
ii) a sealing member, that prior to sealing has a transverse dimension greater than a transverse dimension of the said channel shaped portion;
iii) whereby, in use, in order to effect a seal, the second housing part can be moved relative to the said first housing part causing the sealing member to be inserted into the channel shaped portion of the first housing part, and thereby compressed in its transverse dimension.
In preferred embodiments of the invention, the first and second housing parts can be cylindrical. The sealing member is preferably annular. For these embodiments, the transverse compression of the sealing member is specifically radial compression. The first and second housing parts may also be linear, i.e. made of shapes with substantially straight edges. For these embodiments, the sealing member(s) is preferably also straight, with or without bends or rounds to accommodate corners of the housing.
The sealing member may, but need not be, inserted into the channel shaped portion of the first housing member such that it contacts the base of the channel shaped portion. If it does do so, then there may be an axial seal formed between the channel base and the sealing member, in addition to the transverse seal formed by compression of the sealing member in its transverse dimension. However, a major advantage of the present invention is that no axial compression is required for good sealing action.
Preferably the channel shaped portion is defined by an opening, two side walls and a base. Preferably the side walls extend substantially perpendicularly to the base, and the channel shaped portion is substantially uniform in its width (i.e. the distance between the side walls is substantially uniform) along its depth, and also along its length.
Preferably the sealing member is inserted into the channel shaped portion so that the nearest point of contact between the sealing member and the inner side wall of the channel shaped portion is at least 1 mm from the opening of the channel shaped portion, preferably at least 3 mm, especially preferably at least 5 mm, or even at least 10 mm or more, depending on the overall dimensions of the parts. This advantageously allows for some axial movement (i.e. in the opening/closing direction) between the housing parts, during operation, without any loss of sealing, since the sealing member can move the maximum 1, 3, 5, or even 10 mm before sealing contact is lost. It also allows a less strong clamping system to be used to hold the housing parts together, compared to the case where the point of sealing between the sealing member and the inner wall of the channel shaped housing is at the opening of the channel, and compared to longitudinal seals, where any relative longitudinal movement between the housing parts would reduce the seal formed.
The second housing part is preferably moved towards the first housing part in a direction that is substantially perpendicular to the said transverse dimension of the sealing member, and preferably in a direction that is substantially perpendicular to the direction of compression of the sealing member.
An advantage of the transverse sealing arrangement of the present invention (e.g. where the direction of relative movement of the housing parts is perpendicular to the direction of compression of the sealing member) is that relatively low closing forces are to be applied and maintained by the closing system (e.g. a clamp or latches), compared to axial sealing arrangements (in which the direction of relative movement of housing parts is the same as the direction of compression of the sealing part). This is because in transverse sealing arrangements, the seal compression is not in the same direction as the closing direction of the housing parts.
In preferred aspects of the invention, the second housing part comprises a tongue shaped portion, which in the method of the invention is inserted into the channel shaped portion in order to insert the sealing member into the channel shaped portion of the first housing part. The arrangement is then a tongue and groove arrangement.
In the sealing arrangement of the present invention the critical dimensions for ensuring a good seal are the relative dimensions of the channel shaped portion and the sealing member; and for embodiments where the second housing part is a tongue shaped member, the thickness of the tongue. The sealing arrangements according to the invention allow for a slight relative movement of both housing parts without loss of compression of sealing. Thus closing, and manufacture of the parts that hold the housing part together are less craft sensitive, and less dependent on manufacturing and design tolerances. Therefore manufacture of the housing parts is much cheaper.
Preferably, as the sealing member is compressed, it is compressed into sealing contact with both inner side walls of the channel shaped portion of the first housing part, i.e. with two surfaces of the first housing part. Especially preferably, as the sealing member is compressed it is also urged into sealing contact with two surfaces of the second housing part. For example, where the second housing part comprises a tongue shaped member, the sealing member is preferably compressed so that it extends within the passage between the tongue and the groove (channel), and seals to both side surfaces of the tongue, and both inner walls of the groove. Similarly, where in another embodiment, both housing parts comprise channel shaped members, the sealing arrangement is preferably arranged to be compressed into sealing engagement with both inner walls of each channel shaped portion. In these embodiments, and in all the specific embodiments described below with reference to the drawings there are at least two sealing barriers between the upper and lower (first and second) housing parts, providing extra reliability against accidental damage.
Since the seals are transverse rather than axial, there is no need to put any significant force on the housing parts to push them together in the axial direction. This means that those parts of the housing, which in an axial design would need to be reinforced, need not be reinforced. This results in a simpler, cheaper design.
One embodiment of the invention comprises a first housing part that has a mating surface that comprises a channel shaped portion; a second housing part that has a cooperating mating surface comprising a tongue which can fit loosely into the channel; and a sealing member that is generally xe2x80x9cUxe2x80x9d or xe2x80x9cVxe2x80x9d shaped in cross-section, with an O ring portion at the tip of each arm of the xe2x80x9cUxe2x80x9d or xe2x80x9cVxe2x80x9d. The sealing member is shaped so that it can be positioned over the tongue of the second housing member, and inserted into the channel of the first housing member, by moving the tongue of the second housing part into the channel of the first housing part. Prior to insertion the O-ring seals, at the tip of each arm of the xe2x80x9cUxe2x80x9d or xe2x80x9cVxe2x80x9d, project laterally beyond the edges of the opening of the channel, and when inserted, they are therefore radially compressed. They make contact with both inner walls of the channel of the first housing part, and both outer walls of the tongue of the second housing part. Therefore they make contact with two surfaces on each of the housing parts.
In another embodiment according to the invention, the first and second housing parts are as described above, but the sealing member is a generally flat sheet having a thickness greater, preferably at least 10% greater than the nominal gap between tongue and channel, (i.e. greater than 10% of ((width channel-thickness tongue)/2)), more preferably at least 20% greater, or even 50% greater, than the said nominal gap, for certain materials. The flat sealing member is positioned over the opening of the channel, and the tongue brought towards it to urge it into the channel, and thereby compress it between the outer walls of the tongue and the inner walls of the channel. The sealing member contacts both inner walls of the channel, and both outer walls of the tongue. Therefore the sealing member contacts two surfaces on each of the housing parts.
In both the above embodiments using tongue and groove shaped housing parts, a single sealing member extending around the tongue shaped portion is used. In both cases, prior to insertion in the channel, the overall transverse dimension of the sealing member is greater than a transverse dimension of the channel. In the first case, for the xe2x80x9cUxe2x80x9d or xe2x80x9cVxe2x80x9d shaped sealing member, with an O-ring seal at the tip of each arm of the xe2x80x9cUxe2x80x9d or xe2x80x9cVxe2x80x9d the distance from the extreme outward facing side of one O-ring seal, to the extreme outward facing side of the other O-ring seal is greater than a width of the channel. In the second case, for the flat sheet sealing member, the width of the sealing member, prior to insertion in the channel is greater than the width of the channel.
For tongue and groove shaped housing parts, a critical feature is the width of the transverse gap (i.e. the gap to the side of the tongue) between the tongue and groove (channel) relative to the dimension of the sealing member that will be positioned in that gap.
A third aspect of the present invention therefore provides a method of forming a seal between a first channel shaped housing part, and a second tongue shaped housing part, the method comprising:
i) providing one or more sealing member(s), that prior to sealing have a dimension greater than any transverse gap(s) between tongue and channel shaped housing parts;
ii) positioning the sealing member(s) in the gap between the tongue and the channel shaped housing parts, by moving the tongue shaped housing part relative to the channel shaped housing part, causing the sealing member to be compressed between the tongue shaped housing part, and the channel shaped housing part.
A fourth aspect of the present invention provides a sealing arrangement comprising:
i) a first channel shaped housing part and a second tongue shaped housing part; and
ii) one or more sealing members, that prior to sealing have a dimension greater than any transverse gap(s) between the tongue shaped housing part and the channel shaped housing part;
whereby, in use, in order to effect a seal, the tongue shaped housing part can be moved relative to the channel shaped housing part, causing the sealing member(s) to be inserted into the gap(s) between the tongue shaped housing part and the channel shaped housing part, and thereby compressed.
The third and fourth aspects of the invention include the two tongue and groove embodiments described above. For the embodiment comprising a xe2x80x9cUxe2x80x9d or xe2x80x9cVxe2x80x9d shaped sealing member with O-ring seals at the tip of each arm of the xe2x80x9cUxe2x80x9d or xe2x80x9cVxe2x80x9d, said dimension of the sealing member that is greater than any gap between the tongue and channel is the width of each of the O-ring seals. For the embodiment comprising a flat sheet sealing member, the said dimension of the sealing member that is greater than any gap between the tongue and channel is the thickness of the sheet.
The third and fourth aspects of the invention also include other embodiments. For example, the use of two separate sealing members (e.g. O-ring or strip sealing members) urged into the gaps on respective sides of the tongue, but not beneath the tongue. In this case the width of each sealing member would be greater than the width of the respective gap between the channel and tongue. The separate sealing members could, for example, be pre-secured to the tongue shaped sealing member.
Various preferred features of the first and second aspects of the invention also apply to the third and fourth aspect of the invention.
In other embodiments according to the invention both housing parts comprise channel shaped portions and the sealing member extends into both of the channels, and is transversely compressed into sealing engagement with both walls of each channel as the housing parts are brought towards each other. In one embodiment the sealing member, in cross-section, is generally dumbbell shaped, comprising two rib-shaped seals carried at either end of a central, preferably rigid, carrier strip. The sealing ribs have a transverse dimension greater than a transverse dimension of the channel. The channel shaped portions of the two housing parts, may or may not be identical or similar in shape and size. Similarly, the two rib-shaped seals carried at either end of a central carrier strip in the dumbbell shaped sealing member may or may not be identical or similar in shape and size.
In another embodiment, the sealing member, in cross-section, is generally xe2x80x9cIxe2x80x9d shaped, the top and base of the xe2x80x9cIxe2x80x9d being longer than a transverse dimension of the channels and thus providing the sealing contact to both inner walls of each channel. The stem of the I acts as a carrier for the sealing top and base of the xe2x80x9cIxe2x80x9d. Preferably the total surface area of contact of the sides of the top and base of the xe2x80x9cIxe2x80x9d with the channel shaped portions of the housing is less than the surface area of the stem of the xe2x80x9cIxe2x80x9d which is exposed to the either internal or external pressure within the housing. This results in the contact pressure always increasing more than the applied pressure. Therefore applying either an internal or an external pressure to the sealing member will increase the contact force on the sealing surfaces (the sides of the top and base of the xe2x80x9cIxe2x80x9d), i.e. the I shaped embodiment of the invention advantageously self seals when exposed to over-pressure or under-pressure from within the housing. The contact pressure is also enhanced by the fact that the top and base of the xe2x80x9cIxe2x80x9d of the seal are initially compressed. The self-sealing nature of the xe2x80x9cIxe2x80x9d shaped sealing member embodiment is also described later in relation to the specific examples and drawings.
Examples of materials suitable for use as the sealing member of the present invention include plain rubbers, e.g. nitrile rubber, silicon rubber, and EPDM; rubber foam, e.g. closed cell EPDM, silicon; self lubricating rubber, e.g. silicon rubber; gel coated rubber, gel impregnated foam, mastics and gel with or without a carrier. Gels have various advantages, for example they can be highly conformable at room temperature since they can have an almost liquid-like flexibility that allows them to conform to the substrate to be sealed. They have a cross-linked structure which gives them elasticity, cohesive strength, and form stability. The cross-linked structure may result from cross-linking chemical bonds, as in the case of a silicone or polyurethane gel, or it may result from the formation of crystalline regions as in the case of thermoplastic gels such as those based on block copolymers. In any case, the gel will comprise some form of three-dimensional polymer network, extended by means of an oil or other material. Gels are disclosed in U.S. Pat. No. 4,600,261, the disclosure of which is incorporated herein by reference.
Examples of materials suitable for the housing parts include mainly polymers and metal but also composite or ceramic types of materials.
The housing parts and sealing members may be any suitable shape according to the application. For example a circular base housing part and a dome shaped housing part may each have generally annular mating surfaces, and be used in conjunction with a generally annular sealing member. For a generally box shaped housing, housing parts with substantially straight mating surfaces may be used, in conjunction with either several generally straight elongate sealing members along one or more edges, or a generally annular sealing member, bent to form comers to fit the box shape. Thus where it is specified that the sealing member may have a particular cross-sectional shape, e.g. xe2x80x9cVxe2x80x9d or xe2x80x9cIxe2x80x9d or dumbbell, this may apply to a generally straight sealing member, or to a generally annular sealing member.